U.S. patent number 9,631,672 [Application Number 14/917,404] was granted by the patent office on 2017-04-25 for solid-lubrication rolling bearing.
This patent grant is currently assigned to NTN CORPORATION. The grantee listed for this patent is NTN CORPORATION. Invention is credited to Hisanori Aiga, Takahiro Gotou, Yoshinori Ito, Hiroki Manabe, Fuminori Satoji, Naoaki Tsuji.
United States Patent |
9,631,672 |
Aiga , et al. |
April 25, 2017 |
Solid-lubrication rolling bearing
Abstract
A separator 8 including a solid lubricant is disposed between
adjacent rolling elements 7. Relative movement of the adjacent
rolling elements 7 and the separator 8 in a direction of separating
apart in a circumferential direction is restricted by restricting
members 10, and the restricting members 10 are disposed at plural
locations in the circumferential direction. A minute gap .alpha. is
provided between the adjacent restricting members 10, to allow
relative movement therebetween. This can provide a
solid-lubrication rolling bearing capable of stably preventing
rotational locking and unintended disassembling of the bearing for
a long period.
Inventors: |
Aiga; Hisanori (Mie,
JP), Manabe; Hiroki (Mie, JP), Tsuji;
Naoaki (Mie, JP), Gotou; Takahiro (Aichi,
JP), Ito; Yoshinori (Aichi, JP), Satoji;
Fuminori (Aichi, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
NTN CORPORATION |
Osaka |
N/A |
JP |
|
|
Assignee: |
NTN CORPORATION (Osaka,
JP)
|
Family
ID: |
52688862 |
Appl.
No.: |
14/917,404 |
Filed: |
September 16, 2014 |
PCT
Filed: |
September 16, 2014 |
PCT No.: |
PCT/JP2014/074428 |
371(c)(1),(2),(4) Date: |
March 08, 2016 |
PCT
Pub. No.: |
WO2015/041212 |
PCT
Pub. Date: |
March 26, 2015 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
|
US 20160223021 A1 |
Aug 4, 2016 |
|
Foreign Application Priority Data
|
|
|
|
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Sep 19, 2013 [JP] |
|
|
2013-193699 |
Sep 24, 2013 [JP] |
|
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2013-196466 |
Sep 24, 2013 [JP] |
|
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2013-196467 |
Apr 4, 2014 [JP] |
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2014-077916 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16C
33/6696 (20130101); F16C 29/04 (20130101); C10M
161/00 (20130101); F16C 33/80 (20130101); F16C
19/20 (20130101); F16C 33/37 (20130101); C10M
103/02 (20130101); C10M 2201/041 (20130101); C10N
2050/14 (20200501); C10N 2040/02 (20130101) |
Current International
Class: |
F16C
33/37 (20060101); F16C 19/20 (20060101); F16C
33/66 (20060101); C10M 103/02 (20060101); C10M
161/00 (20060101); F16C 29/04 (20060101); F16C
33/80 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2002-70875 |
|
Mar 2002 |
|
JP |
|
3550689 |
|
Aug 2004 |
|
JP |
|
2006-17241 |
|
Jan 2006 |
|
JP |
|
3934277 |
|
Jun 2007 |
|
JP |
|
2012-67884 |
|
Apr 2012 |
|
JP |
|
2013-79715 |
|
May 2013 |
|
JP |
|
2013-87797 |
|
May 2013 |
|
JP |
|
Other References
International Preliminary Report on Patentability and Written
Opinion of the International Searching Authority issued Mar. 22,
2016 in International (PCT) Application No. PCT/JP2014/074428.
cited by applicant .
International Search Report issued Dec. 16, 2014 in International
(PCT) Application No. PCT/JP2014/074428. cited by
applicant.
|
Primary Examiner: Hannon; Thomas R.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
L.L.P.
Claims
The invention claimed is:
1. A solid-lubrication rolling bearing comprising: an outer ring
having an outer raceway face; an inner ring having an inner raceway
face; a plurality of rolling elements disposed between the outer
raceway face and the inner raceway face; and a separator disposed
between the adjacent rolling elements, the separator being formed
of a solid lubricant, wherein relative movement of the adjacent
rolling elements and the separator in a direction of separating
apart in a circumferential direction is restricted by restricting
members, and the restricting members are disposed at a plurality of
places in the circumferential direction to allow relative movement
between the adjacent restricting members.
2. The solid-lubrication rolling bearing according to claim 1,
wherein the solid lubricant is formed by molding and firing powder
that includes amorphous and self-sintering carbon material powder,
graphite powder, and a binder.
3. The solid-lubrication rolling bearing according to claim 1,
wherein a receptacle for the solid lubricant powder is provided on
an axial outer side of the restricting member.
4. The solid-lubrication rolling bearing according to claim 3,
further comprising: a seal member disposed on the axial outer side
of the restricting member, the seal member sealing a space between
the inner ring and the outer ring, and a shielding member opposed
to the seal member in an axial direction, the shielding member
extending in a radial direction.
5. The solid-lubrication rolling bearing according to claim 4,
wherein the shielding member is disposed on an axial inner side of
the seal member, and the shielding member forms the receptacle for
the solid lubricant powder.
6. The solid-lubrication rolling bearing according to claim 4,
wherein a labyrinth gap is formed between the shielding member and
the seal member.
7. The solid-lubrication rolling bearing according to claim 1,
further comprising a structure that prevents contact between the
outer ring and the separator.
8. The solid-lubrication rolling bearing according to claim 1,
wherein each of the restricting members includes a bottom portion
extending between the outer ring and the inner ring in the
circumferential direction, and a restricting portion extending from
the bottom portion in a space between the inner raceway face and
the outer raceway face.
9. The solid-lubrication rolling bearing according to claim 8,
wherein an inner side face of each of the bottom portion and the
restricting portion is a flat face having no curvature.
10. The solid-lubrication rolling bearing according to claim 8,
wherein a seal member that seals the space between the inner ring
and the outer ring is disposed on an axial outer side of the bottom
portion of the restricting member.
11. The solid-lubrication rolling bearing according to claim 8,
wherein an outer diameter end and an inner diameter end of the
bottom portion is made close to an inner circumferential face of
the outer ring and an outer circumferential face of the inner
ring.
12. The solid-lubrication rolling bearing according to claim 1,
wherein a pair of the restricting members are disposed on both
axial sides of the rolling element and the separator, and the pair
of restricting members, and the rolling element and the separator
that are accommodated within the restricting members are regarded
as one unit, and the units are disposed at a plurality of places in
the circumferential direction to allow relative movement between
the units.
13. The solid-lubrication rolling bearing according to claim 12,
wherein the restricting members have an identical shape.
14. The solid-lubrication rolling bearing according to claim 1,
wherein the restricting members have an identical shape.
15. The solid-lubrication rolling bearing according to claim 1,
used in a tenter clip of a film stretching machine.
Description
TECHNICAL FIELD
The present invention relates to a solid-lubrication rolling
bearing using a solid lubricant.
BACKGROUND ART
The solid-lubrication rolling bearing is suitable for use at
elevated temperatures or in a vacuum, which prevents use of grease
or lubricating oil as a lubricant, for example, for use as a tenter
clip bearing of a film stretching machine.
The film stretching machine herein is a machine for manufacturing a
stretched film used in general packaging materials, liquid crystal
panels, or secondary batteries. To improve the strength of the
film, as illustrated in FIG. 29, the film stretching machine
continuously transfers a film 100 in a longitudinal direction
(direction of an arrow X), and stretches the film 100 in its width
direction in a region expressed by a broken line while heating the
film 100 (potentially, further stretches the film 100 in its
longitudinal direction). The tenter clip is a mechanical component
in the film stretching machine, which clips both ends of the film,
and stably circulates along a caterpillar guide rail as illustrated
by an arrow C in this figure to stretch the film in a predetermined
direction. The tenter clip bearing is used in a portion that guides
travelling of the tenter clip along the rail at elevated
temperatures (250.degree. C. or higher, and about 400.degree. C. at
maximum). Therefore, it is necessary to use the solid-lubrication
rolling bearing.
In such conventional solid-lubrication rolling bearings, a
separator formed of a solid lubricant is disposed between adjacent
rolling elements without using a retainer (Patent literature 1 and
Patent literature 2). In another conventional solid-lubrication
rolling bearing, a retainer holds the separator and the rolling
elements with rivets (Patent literature 3).
CITATION LIST
Patent Literature
Patent literature 1: U.S. Pat. No. 3,934,277
Patent literature 2: Japanese Unexamined Patent Application
Publication No. 2012-67884
Patent literature 3: U.S. Pat. No. 3,550,689
SUMMARY OF THE INVENTION
Technical Problems
During the use of the solid-lubrication rolling bearing, the
separator formed of solid lubricant is subjected to wear or crack
due to contact with the rolling elements, and becomes gradually
small. Thus, with the configuration having no retainer as described
in Patent literature 1 and Patent literature 2, when the separator
becomes small after long-term use, the rolling elements may be
unevenly distributed in a partial circumferential region.
Especially when all of the rolling elements move to a
circumferential region of 180 degrees or less, the inner ring is
separated from the outer ring with a small external force, and the
bearing is disassembled unintendedly to be disabled. On the
contrary, with the configuration described in Patent literature 3,
the retainer keeps a distance between the adjacent rolling elements
to avoid the above-mentioned trouble. However, in an initial state
where the separator does not wear, since the degree of freedom of
position between the rolling elements and the retainer is small,
the wear powder of the separator is readily filled in gaps between
a pocket face of the retainer and the rolling elements. This can
obstruct rotation and revolution of the rolling elements to cause
rotational locking.
An object of the present invention is to provide a
solid-lubrication rolling bearing capable of stably preventing
rotational locking and unintended disassembling of the bearing for
a long period.
Solution to Problems
A solid-lubrication rolling bearing according to the present
invention includes: an outer ring having an outer raceway face; an
inner ring having an inner raceway face; a plurality of rolling
elements disposed between the outer raceway face and the inner
raceway face; and a separator disposed between the adjacent rolling
elements, the separator being formed of a solid lubricant, relative
movement of the adjacent rolling elements and the separator in a
direction of separating apart in a circumferential direction is
restricted by restricting members, and the restricting members are
disposed at a plurality of places in the circumferential direction
to allow relative movement between the adjacent restricting
members.
With such configuration, a moving range of each rolling element in
the circumferential direction is restricted by the restricting
members. For this reason, even when the separator becomes smaller
due to wear caused by the operation of the bearing, all of the
rolling elements are prevented from being unevenly distributed in a
partial circumferential region. Thus, the outer ring is not
separated from the inner ring even after long-term operation,
preventing unintended disassembling of the bearing.
Since the restricting members can individually move, the size of a
gap between the rolling element and an inner side face of the
restricting member can be flexibly changed. For this reason,
discharging the solid lubricant powder accumulated in the gap can
be promoted, preventing the gap from being filled with the solid
lubricant powder to cause rotational locking. Since the restricting
members are not connected to each other with a connecting member
such as a rivet, there is no need to ensure a set-up space for the
connecting member in the bearing in the circumferential direction.
Thus, many rolling elements can be assembled in the bearing to
increase a basic rated load of the bearing. Moreover, the operation
of connecting the restricting members to each other becomes
unnecessary, reducing man-hour at assembling of the bearing.
Preferably, the solid lubricant is formed by molding and firing
powder that includes amorphous and self-sintering carbon material
powder, graphite powder, and a binder.
The carbon material powder used in the solid lubricant is different
from crystalline graphite due to its amorphous property, and is
different from non self-sintering carbon fiber due to its
self-sintering property. Examples of the amorphous and
self-sintering carbon material powder include pitch powder and coke
powder. Such carbon material powder is hardened by firing, and
forms a skeleton structure in which adjacent carbon material
particles are combined with each other after firing due to the
self-sintering property. The graphite particles are held by the
skeleton structure and thus, are hard to fall off. This can
increase material strength and improve impact resistance and wear
resistance.
A receptacle for the solid lubricant powder, which is provided on
the axial outer side of the restricting member, can catch excess
solid lubricant powder, thereby preventing leakage of the solid
lubricant powder to the outside of the bearing.
In this case, the solid-lubrication rolling bearing may be further
provided with a seal member that is disposed on the axial outer
side of the restricting member and seals the space between the
inner ring and the outer ring, and a shielding member that is
opposed to the seal member in an axial direction and extends in a
radial direction. When the shielding member extending in the radial
direction is disposed on the axial outer side of the restricting
member, solid lubricant powder generated in the separator hardly
reaches the seal member, thereby effectively preventing leakage of
the solid lubricant powder. The shielding member can also prevent
fall-off of the restricting member.
The shielding member can be disposed on the axial inner side of the
seal member to form a receptacle for the solid lubricant powder.
For example, a recessed portion can be formed on the axial inner
side face of the shielding member, or a recess can be formed
between an axial outer side face of the shielding member and the
seal member to form the receptacle for the solid lubricant
powder.
A labyrinth gap is formed between the shielding member and the seal
member, so that leakage of the solid-lubrication powder to the
outside of the seal member is prevented more effectively.
Preferably, the solid-lubrication rolling bearing is provided with
a structure that prevents contact between the outer ring and the
separator. Thereby, even when the separator is sandwiched between
the next rolling elements and pressed toward the outer ring, the
solid lubricant in the separator never contacts the outer ring to
cause wear. Thus, during operation of the bearing, especially under
high oscillation or after long-term use, contact of the separator
with the inner circumferential face of the outer ring can be
prevented to eliminate wear more than necessary. The ability of the
solid lubricant can be continuously demonstrated and the life of
the bearing can be extended.
The structure for preventing contact between the separator and the
outer ring may be formed of a metal plate fixed to the separator on
the outer ring side. The structure may be formed of an arm that
extends from the outer diameter end of the restricting member in
the bearing axial direction and is disposed between the separator
and the inner circumferential face of the outer ring, or
male/female fitting between the separator and the restricting
member. In either case, simple configuration can prevent the solid
lubricant portion of the separator from contacting with the inner
circumferential face of the outer ring. Therefore, wear of the
separator is suppressed, so that the life of the separator, in
turn, the solid-lubrication rolling bearing can be extended.
Preferably, the restricting members each are provided a bottom
portion that extends between the outer ring and the inner ring in
the circumferential direction, and a restricting portion that
extends from the bottom portion in a space between the inner
raceway face and the outer raceway face.
When the inner side face of each of the bottom portion and the
restricting portion may be made a flat face having no curvature,
discharge of the solid lubricant through the gap can be further
promoted.
A sealing member that seals the space between the inner ring and
the outer ring can be disposed on the axial outer side of the
bottom portion of the restricting member, preventing the
restricting member from falling off.
By making an outer diameter end and an inner diameter end of the
bottom portion close to an inner circumferential face of the outer
ring and an inner ring of the outer circumferential face, the
bottom portion can keep generated solid lubricant powder around the
raceway face. Thus, leakage of the solid lubricant powder to the
outside of the bearing can be suppressed.
A pair of the restricting members are disposed on both axial sides
of the rolling element and the separator, the pair of restricting
members, and the rolling element and the separator that are
accommodated within the restricting members are regarded as one
unit, and the units are disposed at a plurality of places in the
circumferential direction to allow relative movement between the
units, thereby preventing leakage of the solid lubricant powder to
the outside of the bearing more reliably.
When the restricting members may have the same shape, processing
costs of the restricting members can be reduced to reduce costs of
the solid-lubrication rolling bearing.
The above-mentioned solid-lubrication rolling bearing is especially
suitable as a tenter clip bearing in a film stretching machine.
Advantageous Effects of Invention
The solid-lubrication rolling bearing according to the present
invention can stably prevent rotational locking and unintended
disassembling of the bearing for a long period.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating schematic structure of a
tenter clip.
FIG. 2 is a sectional view illustrating a solid-lubrication rolling
bearing in accordance with a First embodiment.
FIG. 3 is a front view illustrating the solid-lubrication rolling
bearing when viewed from an A direction in FIG. 2.
FIG. 4 is a partial exploded view illustrating the
solid-lubrication rolling bearing in FIG. 2 when viewed from the
outer diameter side, with an outer ring being removed.
FIG. 5 is a perspective view illustrating a restricting member.
FIG. 6 is a sectional view illustrating the solid-lubrication
rolling bearing in accordance with a second embodiment.
FIG. 7 is a front view illustrating the solid-lubrication rolling
bearing when viewed in an A direction in FIG. 6.
FIG. 8 is a partial exploded view illustrating the
solid-lubrication rolling bearing in FIG. 6 when viewed from the
outer diameter side, with an outer ring being removed.
FIG. 9a is a front view illustrating a separator when viewed in the
axial direction.
FIG. 9b is a plan view illustrating the separator in the radial
direction.
FIG. 10 is a sectional view illustrating the solid-lubrication
rolling bearing in accordance with a third embodiment.
FIG. 11 is an exploded view illustrating the solid-lubrication
rolling bearing in FIG. 10 when viewed from the outer diameter
side, with an outer ring being removed.
FIG. 12 is a sectional view illustrating the solid-lubrication
rolling bearing in accordance with a fourth embodiment.
FIG. 13 is an exploded view illustrating the solid-lubrication
rolling bearing in FIG. 12 when viewed from the outer diameter
side, with an outer ring being removed.
FIG. 14 is a sectional view illustrating the solid-lubrication
rolling bearing in accordance with a fifth embodiment.
FIG. 15 is a sectional view illustrating the solid-lubrication
rolling bearing in accordance with a sixth embodiment.
FIG. 16 is a front view illustrating the solid-lubrication rolling
bearing in FIG. 15, with a shield plate being removed.
FIG. 17 is a partial exploded view illustrating the
solid-lubrication rolling bearing in FIG. 15 when viewed from the
outer diameter side, with an outer ring being removed.
FIG. 18a is a front view illustrating a separator when viewed in
the axial direction.
FIG. 18b is a plan view illustrating the separator when viewed from
the outer diameter side.
FIG. 19 is a sectional view illustrating the solid-lubrication
rolling bearing in accordance with a seventh embodiment.
FIG. 20 is a front view illustrating the solid-lubrication rolling
bearing in FIG. 19, with a shield plate being removed.
FIG. 21 is a partial exploded view illustrating the
solid-lubrication rolling bearing in FIG. 19 when viewed from the
outer diameter side, with an outer ring being removed.
FIG. 22 is a sectional view illustrating the solid-lubrication
rolling bearing in accordance with an eighth embodiment.
FIG. 23 is a front view illustrating the solid-lubrication rolling
bearing in FIG. 22, with a shield plate being removed.
FIG. 24 is a partial exploded view illustrating the
solid-lubrication rolling bearing in FIG. 22 when viewed from the
outer diameter side, with an outer ring is removed.
FIG. 25a is a front view illustrating a separator in FIG. 22 when
viewed in the axial direction.
FIG. 25b is a plan view illustrating the separator in FIG. 22 when
viewed from the outer diameter side.
FIG. 25c is a side view illustrating the separator in FIG. 22 when
viewed in the circumferential direction.
FIG. 26 is a view illustrating microstructure of a solid lubricant
used in the solid-lubrication rolling bearing of the present
invention.
FIG. 27 is a sectional view illustrating configuration of
granulated powder used in a manufacturing process of the solid
lubricant.
FIG. 28 is a view illustrating microstructure of a conventional
solid lubricant.
FIG. 29 is a plan view illustrating schematic configuration of a
film stretching machine.
DESCRIPTION OF EMBODIMENTS
Configuration of the present invention will be described below with
reference to FIG. 1 to FIG. 28.
FIG. 1 illustrates schematic structure of a tenter clip of a film
stretching machine, to which a solid-lubrication rolling bearing
according to the present invention can be applied. As described
above, the tenter clip moves under guide of a caterpillar guide
rail 1, and includes a frame 2, a clip 3 that clips a film 100 (See
FIG. 29), and a plurality of bearings 4 rotatably supported by the
frame 2. The tenter clip is driven by a chain not illustrated to
travel. At this time, an outer circumferential face of each of the
bearings 4 rolls on the guide rail 1, thereby moving the tenter
clip along the guide rail 1 to stretch a film clipped by the clip
3. Another ring-like member engaged with an outer circumferential
face of an outer ring of the bearing may roll on the guide rail
1.
First Embodiment
FIG. 2 is a sectional view illustrating a solid-lubrication rolling
bearing 4 for a tenter clip in accordance with a first embodiment,
and FIG. 3 is a front view of the bearing 4 in FIG. 2 when viewed
from an A direction (however, a right shield plate 9 in FIG. 2 is
removed). The bearing 4 is shaped as a deep groove ball bearing,
and includes, as main constituents, an outer ring 5 having an outer
raceway face 5a on its inner circumferential face, an inner ring 6
having an inner raceway face 6a on its outer circumferential face,
a plurality of (six in this embodiment) rolling elements 7 such as
balls disposed between the outer raceway face 5a and the inner
raceway face 6a, a plurality of (six in this embodiment) separators
8 disposed between the adjacent rolling elements 7, and a sealing
member 9 that seals a space between the outer ring 5 and the inner
ring 6 on both axial sides. In the bearing 4 in this embodiment,
the outer circumferential face 5b of the outer ring 5 becomes a
rolling face that rolls on the guide rail 1 in FIG. 1, and an inner
circumferential face 6b of the inner ring 6 fixedly engages with a
fixed shaft 2a provided at the frame 2.
The sealing member 9 is formed of a shield plate, for example. An
outer diameter end of the shield plate 9 is fixedly press-fitted
into a circumferential groove in the inner circumferential face of
the outer ring 5, and an inner diameter end of the shield plate 9
comes close to the outer circumferential face of the inner ring 6.
This configuration forms a non-contact seal. A contact seal may be
formed by bringing the inner diameter end of the sealing member 9
into slide contact with the outer circumferential face of the inner
ring 6.
The outer ring 5, the inner ring 6, and the rolling elements 7 are
made of steel, for example, martensitic stainless steels such as
SUS440C. The rolling elements may be made of ceramics, and examples
of the ceramics include silicon nitride. When the rolling elements
7 are not made of ceramics, the rolling elements 7 are preferably
coated with a solid-lubrication material such as graphite.
Preferably, the shield plate 9 is made of steel, for example,
austenitic stainless steels such as SUS304 having excellent
corrosion resistance.
The separator 8 is formed of solid lubricant. The solid lubricant
may have any composition. For example, the separators 8 may be made
of a solid-lubrication material including a layered substance such
as graphite, molybdenum disulfide, and tungsten disulfide, soft
metal such as gold, silver, and lead, or polymer resin composite
such as PTFE and polyimide, or a composite material containing the
solid-lubrication material as a main ingredient. For example, the
separators 8 may be formed by molding and firing graphite powder,
or molding and firing powder containing graphite as a main
ingredient along with a binder.
The separators 8 may have any shape, and in this embodiment, the
separators 8 each are partially cylindrical. The thickness of the
separator 8 in the radial direction is slightly smaller than a
difference between a radius of the inner circumferential face of
the outer ring 5 (shoulder face 5c adjacent to the outer raceway
face 5a) and a radius of the outer circumferential face of the
inner ring 6 (shoulder face 6c adjacent to the inner raceway face
6a). An axial dimension of the separator 8 is larger than an axial
dimension of the outer raceway face 5a and the inner raceway face
6a. Accordingly, during rotation of the bearing, the outer
circumferential faces and the inner circumferential faces of the
separators 8 at both axial ends can slidingly contact the shoulder
faces 5c, 6c of the outer ring 5 and the inner ring 6.
In FIG. 3, inner circumferential faces 8a (faces opposed to the
outer circumferential face of the inner ring 6) and outer
circumferential faces 8b (faces opposed to the inner
circumferential face of the outer ring 5) of the separators 8 each
are a cylindrical face using the axis as the center. However, as
illustrated in FIG. 9a and FIG. 9b, a flat face 8c may be formed in
a circumferential central region of the outer circumferential faces
8b of the separator 8.
The solid-lubrication rolling bearings 4 each further include, as a
main constituent, restricting members 10 that hold the adjacent
rolling element 7 and separator 8 from both circumferential sides
to restrict relative movement of the rolling element 7 and
separator 8 in a direction of separating apart in the
circumferential direction. Configuration of the restricting members
10 will be described below in detail with respect to FIG. 4 and
FIG. 5. FIG. 4 is a partial exploded view illustrating the
solid-lubrication rolling bearing 4 in FIG. 2 when viewed from the
outer diameter side, with the outer ring 5 being removed, and FIG.
5 is a perspective view illustrating the restricting member 10.
As illustrated in FIG. 4 and FIG. 5, the restricting members 10
each have a bottom portion 10a extending between the outer ring 5
and the inner ring 6 in the circumferential direction, and
restricting portions 10b extending from both circumferential ends
of the bottom portion 10a in a direction perpendicular to the face
of the bottom portion 10a (axial direction), in an integral manner.
All of inner side face 10a1 of the bottom portion 10a and the inner
side faces 10b1 of the restricting portions 10, which are opposed
to the rolling elements 7 and the separator 8, are flat faces
having no curvature. As illustrated in FIG. 4, an axial length L of
the restricting portion 10b (especially, inner side face 10b1) is
slightly larger than a diameter Db of the rolling element 7 and an
axial dimension P of the separator 8 (L>Db, L>P).
The restricting members 10 each have a thickness of about 0.1 mm to
1.0 mm (in FIG. 2 to FIG. 4, for clarity, the thickness of the
restricting member 10 is exaggerated), and can be manufactured by
pressing, for example, a metal thin plate. The restricting members
10 may be made of any material, for example, an iron-based material
such as stainless steel, or iron-based material coated with
chromium plating or the like for ensuring corrosion resistance.
Alternatively, the restricting members 10 may be formed of any
solid lubricant.
As illustrated in FIG. 2 and FIG. 3, the bottom portion 10a of the
restricting member 10 is disposed between the inner circumferential
face of the outer ring 5 and the outer circumferential face of the
inner ring 6, and the restricting portions 10b are disposed in a
space between the outer raceway face 5a of the outer ring 5 and the
inner raceway face 6a of the inner ring 6. Specifically, the bottom
portion 10a extends between the inner circumferential face of the
outer ring 5 and the outer circumferential face of the inner ring 6
in the bearing circumferential direction, and is perpendicular to
the rotational center of the bearing. The restricting portions 10b
extend from both circumferential ends of the bottom portion 10a in
the bearing axial direction, and cross the revolution track of the
rolling element 7. At least one rolling element 7 and at least one
separator 8 are disposed between the two restricting portions 10b
of the restricting member 10. In this embodiment, the two rolling
elements 7 are disposed between the two restricting portions 10b
restricting member 10, and one separator 8 is disposed between the
two rolling elements 7. That is, the two rolling elements 7 and one
separator 8 are arranged as one set. A circumferential size of the
inner side faces 10b1 of the two restricting portions 10b of the
restricting member 10 is set such that the rolling elements 7 and
the separator 8 between the inner side faces 10b1 can slightly move
in the circumferential direction.
As illustrated in FIG. 3 and FIG. 4, the restricting members 10 are
continuously disposed at a plurality of (preferably, three or more)
places in the circumferential direction. At this time, all of the
restricting members 10 have the same shape. No rolling element 7
and separator 8 are disposed between the restricting portions 10b
of the adjacent restricting members 10, and the restricting
portions 10b are opposed to each other in the circumferential
direction. Accordingly, all of the rolling elements 7 and the
separators 8 are disposed between a pair of the restricting
portions 10b of any restricting member 10. The adjacent restricting
members 10 are not connected to each other, and as illustrated in
FIG. 4, a circumferential minute gap .alpha. is present between the
opposed restricting portions 10b of the adjacent restricting
members 10. For this reason, the adjacent restricting members 10
can move with respect to each other in the circumferential
direction.
A radial dimension of the restricting member 10 is slightly smaller
than a difference between a radius of the shoulder face 5c of the
outer ring 5 and a radius of the shoulder face 6c of the inner ring
6, and the outer diameter end and the inner diameter end of the
bottom portion 10a are close to the inner circumferential face
(shoulder face 5c) of the outer ring 5 and the outer
circumferential face (shoulder face 6c) of the inner ring 6,
respectively. In this embodiment, a gap between the inner diameter
end of the bottom portion 10a and the shoulder face 6c of the inner
ring 6 is smaller than a gap between the outer diameter end of the
bottom portion 10a and the shoulder face 5c of the outer ring 5.
The minute gap .alpha. between the adjacent restricting members 10
can be set such that the inner diameter end of the bottom portion
10a do not contact the outer circumferential face (shoulder face
6c) of the inner ring 6. However, the gap may be set such that the
inner diameter end of the bottom portion 10a temporarily contacts
the outer circumferential face (shoulder face 6c) of the inner ring
6 during rotation of the restricting member 10, if this causes no
problem. Since the bottom portion 10a is thick in FIG. 2, the outer
diameter end of the bottom portion 10a contacts the shield plate 9,
and do not contact the inner circumferential face of the outer ring
5 (shoulder face 5c). However, thinning the bottom portion 10a may
cause the outer diameter end of the bottom portion 10a to contact
the inner circumferential face of the outer ring 5.
The restricting members 10 are assembled between the outer ring 5
and the inner ring 6 in the same orientation such that the bottom
portions 10a are disposed on one axial side of the bearing. The
restricting members 10 may be equally oriented, or may be partially
turned (for example, alternatively turned). The restricting members
10 may be assembled in any stage before or after assembling the
rolling elements 7 and the separators 8 between the outer ring 5
and the inner ring 6. Upon completion of assembling of the rolling
elements 7, the separators 8, and the restricting members 10, the
shield plate 9 is press-fitted into a circumferential groove of the
outer ring 5 to complete the solid-lubrication rolling bearing 4
illustrated in FIG. 2. In this state, since the restricting members
10 are constrained by the sealing member 9 from the axial outer
side, the restricting members 10 do not fall out of the bearing 4.
To constrain movement of the restricting members 10 to the opening
side (right side in FIG. 2), a ring-like member may be attached to
the outer ring 5 (or the inner ring 6) and the member is disposed
between the right shield plate 9 and a front end of the restricting
portion 10a to contact the front end of the restricting portion
10a.
In the solid-lubrication rolling bearing 4 thus configured, during
rotation of the bearing, the rotating and revolving rolling element
7 contact the separator 8, so that the separator 8 are shaved to
generate solid lubricant powder (including small pieces of the
solid lubricant). The solid lubricant powder is transferred and
attached onto the outer raceway face 5a and the inner raceway face
6a. Therefore, the bearing 4 are stably lubricated without
lubricating oil, grease, or the like.
The separators 8 become smaller during operation of the bearing due
to wear. In this case, however, since the moving range of each
rolling element 7 in the circumferential direction is restricted by
the restricting members 10, all of the rolling elements 7 are
prevented from being unevenly distributed in a partial
circumferential region. For this reason, the outer ring 5 is not
separated from the inner ring 6 after long-term operation, thereby
preventing unintended disassembling of the bearing. When three or
more restricting members 10 are used as in this embodiment, the
situation where all of the rolling elements 7 move in a region of
180 degrees or less never occurs theoretically. Thus, the above
trouble can be reliably prevented.
With such configuration, the restricting members 10 can relatively
move in all directions (axial direction, circumferential direction,
and radial direction). Consequently, even in an initial stage (wear
of the separators 8 does not worsen), dimension of gaps between the
rolling element 7, and the inner side faces 10a1, 10b1 of the
restricting member 10 can be flexibly changed. Thus, discharging of
the solid lubricant powder accumulated in the gaps can be promoted,
so that the solid lubricant powder can be prevented from filling
the gaps to cause rotational locking. The effect of promoting
discharging of the solid lubricant powder from the gaps can be
further enhanced by forming the inner side face 10a1 of the bottom
portion 10a and the inner side faces 10b1 of the restricting
portions 10b as flat faces having no curvature.
Since a connecting member such as a rivet used in the bearing in
Patent literature 3 becomes unnecessary, there is no need to ensure
a set-up space for the connecting member in the circumferential
direction. Thus, many rolling elements 7 can be incorporated in the
bearing to increase the basic rated load of the bearing. Further,
the operation of connecting the restricting members 10 to each
other becomes unnecessary, so that man-hour at assembling of the
bearing can be reduced to achieve cost reduction.
Further, since the outer diameter end and the inner diameter end of
the bottom portion 10a of the restricting members 10 are made close
to the inner circumferential face of the outer ring 5 and the outer
circumferential face of the inner ring 6, the bottom portion 10a
can shield the solid lubricant powder generated by contact between
the rolling elements 7 and the separators 8 to keep the solid
lubricant powder near the raceway faces 5a, 6a. Thus, leakage
(especially, leakage to the left in FIG. 2) of the solid lubricant
powder to the outside of the bearing can be reliably prevented.
Since the restricting members 10 have the same shape, processing
costs of the restricting members 10 can be reduced, so that costs
of the solid-lubrication rolling bearings 4 can be further
reduced.
Second Embodiment
Next, a solid-lubrication rolling bearing in accordance with a
second embodiment of the present invention will be described with
reference to FIG. 6 to FIG. 8.
In the second embodiment, a pair of the restricting members 10, 10'
are disposed on one axial side of the rolling elements 7 and the
separators 8. Detailed configuration of this embodiment will be
described below. In the second embodiment, portions of the
restricting members 10' on the other axial side, out of the pair of
restricting members 10, 10', which correspond to portions of the
restricting members 10 on one axial side, are given common
reference numerals followed by symbol (').
In the second embodiment, in the pair of restricting members 10,
10', the bottom portion 10a, 10a' are opposed to each other in the
axial direction, and the restricting portions 10b, 10b' are opposed
to each other in the circumferential direction. The pair of
restricting members 10, 10' are not connected to each other. The
same number of rolling elements 7 and separator 8 as the rolling
elements 7 and separator 8 in the first embodiment are stored in a
space surrounded with inner side faces 10a1, 10a1' of the bottom
portions 10a, 10a', the inner side faces 10b1 of the restricting
portions 10b of the restricting member 10 on one axial side, and
inner side faces 10b1' of the restricting portions 10b' of the
restricting member 10' on the other axial side. An axial length L
of each of the restricting portions 10b, 10b' (a minimum axial
distance between the inner side faces 10a1, 10a1' of the opposed
bottom portion 10a, 100 is slightly larger than a diameter Db of
the rolling element 7 and an axial dimension P of the separator 8
(L>Db, L>P), such that front ends of the restricting portions
10b, 10b' can contact the bottom portions 10a', 10a of the
corresponding restricting members.
In the bearing 4 in this embodiment, the pair of restricting
members 10, 10', the rolling elements 7, and the separator 8 are
used as one unit, and the units are disposed at a plurality of
places (three places in the figure) in the circumferential
direction. A minute gap .alpha. being the same as the first
embodiment is formed between the adjacent units in the
circumferential direction. The other configuration is the basically
same as that in the first embodiment.
The configuration in the second embodiment can achieve the same
effect as the configuration in the first embodiment. The
restricting members 10, 10' are prevented from falling off by
shield plates 9 on both axial sides. With the configuration in the
second embodiment, since the bottom portion 10a, 10a' are disposed
on the both axial sides of the rolling elements 7 and the separator
8, leakage of the solid lubricant powder to both axial sides can be
suppressed, thereby preventing leakage of the solid lubricant to
the outside of the bearing more reliably. Although the restricting
portions 10b, 10b' of the pair of restricting members 10, 10' are
loosely engaged with each other, the restricting portions 10b, 10b'
may be tightly engaged with each other to integrate the unit.
Next, a third to fifth embodiments of the solid-lubrication rolling
bearings 4 according to the present invention will be described
with reference to FIG. 10 to FIG. 14. The third to fifth embodiment
can prevent leakage of the solid lubricant powder into the outside
of the bearing more stably.
Third Embodiment
As illustrated in FIG. 10 and FIG. 11, a solid-lubrication rolling
bearings 4 in a third embodiment basically have the same
configuration as that of the solid-lubrication rolling bearing in
the first embodiment (FIG. 2). However, this embodiment is
different from the first embodiment in that two types of shielding
members 20, 23 extending in the radial direction are provided as
main constituents.
Both of the two types of shielding members 20, 23 are thin and
annular, and are disposed on both axial sides of the sealing member
9 as opposed to the sealing member 9 in the axial direction.
Hereinafter, out of the two types of shielding members 20, 23, the
shielding member 20 located on the axial inner side of the sealing
member 9 is referred to as "first shielding member", and the
shielding member 23 located on the axial outer side is referred to
as "second shielding member". The first shielding member 20 and the
second shielding member 23 as one set are disposed on both axial
sides of the bearing 4. In the third embodiment, the inner diameter
end of the sealing member 9 straightly extends in the radial
direction.
An annular recess 21 is formed in the axial inner side face of the
first shielding member 20. As described later, the recess 21
functions as a receptacle 22 for the solid lubricant powder. The
axial outer side face of the first shielding member 20 is a flat
face extending in the radial direction. The first shielding members
20 are loose-fitted to seal faces 6d formed at both axial ends of
the inner circumferential face of the inner ring 6, and can
slightly move in the axial direction within the range of contact
with the restricting members 10 and the seal member. The first
shielding members 20 can be fixed to the respective seal faces 6d
of the inner ring by press-fitting or the like. In this case, a
minute axial gap is formed between the axial outer side face of the
first shielding member 20 and the axial inner side face of the
opposing sealing member 9.
The second shielding members 23 each are disc-shaped such that both
axial faces are flat faces extending in the radial direction. The
second shielding member 23 is fixed to the seal face 6d of the
inner ring 6 by press-fitting or the like, with a minute axial gap
between its axial inner side face and the axial outer side face of
the sealing member 9.
The restricting members 10 are assembled between the outer ring 5
and the inner ring 6 in the same orientation such that the bottom
portions 10a are disposed on one axial side of the bearing. The
restricting members 10 may be assembled in any stage before or
after assembling the rolling elements 7 and the separators 8
between the outer ring 5 and the inner ring 6. Upon completion of
assembling of the rolling elements 7, the separators 8, and the
restricting members 10, the first shielding members 20 are
assembled, the shield plate 9 is fixedly press-fitted into a
circumferential groove of the outer ring 5, and the second
shielding member 23 is fixedly press-fitted into a small-diameter
face 6d of the inner ring 6 to complete the solid-lubrication
rolling bearing 4 illustrated in FIG. 10. In this state, since the
restricting members 10 are constrained by the sealing member 9 via
the first shielding members 20 from the axial outer side, the
restricting members 10 do not fall out of the bearing 4.
In the solid-lubrication rolling bearing 4 thus configured, during
rotation of the bearing, the rotating and revolving rolling element
7 contact the separator 8, so that the separator 8 formed of the
solid lubricant 11 is shaved to generate solid lubricant powder
(including small pieces of the solid lubricant). The solid
lubricant powder is transferred and attached onto the outer raceway
face 5a and the inner raceway face 6a, so that the bearing 4 is
stably lubricated without lubricating oil, grease, or the like.
If excess solid-lubrication powder is generated in the bearing, the
excess solid lubricant powder is caught and stored in the
receptacles 22 of the first shielding members 20 provided on the
axial outer side of the restricting member 10. For this reason, the
solid lubricant powder is hard to reach the seal gap between the
sealing member 9 and the small-diameter face 6d of the inner ring
6, so that leakage of the solid lubricant powder to the outside of
the bearing can be suppressed.
In addition, an axial gap between the axial outer side face of the
first shielding member 20 and the axial inner side face of the
sealing member 9, an axial gap between the axial inner side face of
the second shielding member 23 and the axial outer side face of the
sealing member 9, and a seal gap between the inner diameter end of
the sealing member 9 and the seal face 6d constitute a
communicating labyrinth gap. The labyrinth gap further enhance the
sealing effect, thereby preventing leakage of the solid lubricant
powder to the outside of the bearing more reliably. Thus, when the
solid-lubrication rolling bearing 4 is used as a tenter clip
bearing, degrading of the film due to leakage of the solid
lubricant powder to the outside can be prevented.
Fourth Embodiment
Next, a fourth embodiment will be described with reference to FIG.
12 and FIG. 13. A solid-lubrication rolling bearing 4 in the fourth
embodiment is configured by adding two types of shielding members
20, 23 extending in the radial direction as in the third embodiment
to the solid-lubrication rolling bearing 4 in the second embodiment
in which the restricting members 10, 10' are disposed on both axial
sides of the rolling elements 7 and the separators 8 (See FIG. 6 to
FIG. 8). The configuration of the fourth embodiment can achieve the
same effects as that of the third embodiment.
Fifth Embodiment
Next, a fifth embodiment of the present invention will be described
with reference to FIG. 14. In the fifth embodiment, the shape of
the labyrinth gap in the fourth embodiment is modified.
As illustrated in FIG. 14, in the fifth embodiment, the axial inner
side face of the first shielding member 20 is a flat face
straightly extending in the radial direction. A protruding portion
24 protruding toward the axial outer side is formed on an inner
radial portion of the axial outer side face of the first shielding
member 20. The inner diameter end of the sealing member 9 is bent
toward the axial inner side so as to conform to the inner radial
shape of the protruding portion 24.
In the fifth embodiment, (1) gaps between each of the axial outer
side face of the protruding portion 24, the inner radial face of
the protruding portion 24, and the axial outer side face on the
inner radial side of the protruding portion 24 of the first
shielding member 20, and the inner diameter end of the sealing
member 9, (2) the axial gap between the axial inner side face of
the second shielding member 23 and the axial outer side face of the
sealing member 9, (3) the seal gap between the inner diameter end
of the seal member 9 and the seal face 6d, constitutes a
communicating labyrinth gap. A recess that is wider than the
labyrinth gap is formed between the axial outer side face on the
outer radial side of the protruding portion 24 of the first
shielding member 20 and the axial inner side face of the sealing
member 9, and the recess constitutes the receptacle 22 for the
solid lubricant powder. FIG. 14 illustrates the solid-lubrication
rolling bearing 4 in the fourth embodiment illustrated in FIG. 12,
in which the restricting members 10, 10' are disposed on both axial
sides of the rolling elements 7. However, the first shielding
members 20 and the sealing member 9 in the fifth embodiment can be
also applied to the solid-lubrication rolling bearing 4 in the
third embodiment illustrated in FIG. 10, in which the restricting
member 10 is disposed on one axial side of the rolling elements
7.
Next, sixth to eighth embodiments of the solid-lubrication rolling
bearings 4 according to the present invention will be described
with reference to FIG. 15 to FIG. 25a, FIG. 25b, and FIG. 25c. In
the sixth to eighth embodiment, a structure that prevents contact
between the face of the separator 8 on the outer ring side and the
inner circumferential face 5c of the outer ring 5 is provided.
In the solid-lubrication rolling bearing, in which the separator
formed of the solid lubricant is interposed between the rolling
elements without using a retainer, as described in Patent
literature 1, under high oscillation or during long-term use, the
separator is subjected to a centrifugal force, and further is
biased toward the outer radial side by the adjacent rolling
elements. As a result, the face of the separator on the outer ring
side contacts the inner radial face of the outer ring, and early
wears. As the separator becomes smaller, powder (ex. wear powder)
generated due to wear is accumulated, and the rolling elements are
displaced in the bearing circumferential direction. Since the
separator revolves with the rolling elements, during rotation of
the bearing, the separator can contact the rolling elements and the
outer ring. Since the circumferential speed of the separator is
higher than the rotational speed of the rolling element, contact
between the separator and the inner circumferential face of the
outer ring acts to promote wear of the separator.
Sixth Embodiment
A sixth embodiment will be described below with reference to FIG.
15 to FIG. 18a, and FIG. 18b. The sixth embodiment is based on the
second embodiment (FIG. 6) in configuration of the restricting
members 10, but may be based on the first embodiment (FIG. 2).
The solid-lubrication rolling bearing 4 in the sixth embodiment is
different from the solid-lubrication rolling bearing 4 in the
second embodiment (FIG. 6) in that a structure that prevents
contact between the separator 8 and the inner circumferential face
of the outer ring 5 is provided on the separator 8, and is the
substantially same as the solid-lubrication rolling bearing 4 in
the second embodiment except for the above configuration.
Specifically, a metal plate 58 is fixed to the outer
circumferential face of the separator 8, and the metal plate 58 is
guided by the inner circumferential face 5c of the outer ring 5.
Like the separator 8 illustrated in FIG. 9a, FIG. 9b, this
separator 8 has a flat face 8c at the circumferential center of an
outer circumferential face 8b, and the metal plate 58 forms the
flat face 5c. The metal plate 58 prevents direct contact between
the solid lubricant of the separator 8 and the inner
circumferential face 5c of the outer ring 5. This can prevent wear
of the separator 8 more than necessary. When the rolling elements 7
are made of ceramics having a smaller specific gravity than steel,
a pressing force of the rolling elements 7 to press the separator 8
toward the outer radial side becomes smaller, so that wear of the
separator 8 can be more effectively suppressed.
The metal plate 58 can be fixed to the separator 8 by utilizing
shrinkage of the separator 8 at firing. At this time, as
illustrated in FIG. 18a, FIG. 18b, with dovetail joint or similar
configuration, both members are hardly separated from each other.
That is, a groove having a trapezoidal transverse face extending in
the bearing axial direction is formed in the outer circumferential
face of the separator 8, and the trapezoidal metal plate 58 is
inserted into the groove. Since a base of the trapezoidal
transverse face of the metal plate 58 is longer than a top side,
and the separator 8 is pressed toward the outer ring 5 by the
adjacent rolling elements 7, the metal plate 58 is not readily
separated from the solid lubricant of the separator 8. Examples of
the material for the metal plate 58 include SUS and iron-based
material coated with chrome plating or the like.
Seventh Embodiment
Next, a seventh embodiment of the present invention will be
described with reference to FIGS. 19 to 21.
A bearing 4 in the seventh embodiment is different from the first
embodiment (FIG. 2) in that a structure that prevents contact
between the separator 8 and the inner circumferential face 5c of
the outer ring 5 is provided integrally with the restricting member
10, and is the substantially same as that in the first embodiment
except for the above configuration. To prevent direct contact
between the separator 8 and the inner circumferential face 5c of
the outer ring 5, an arm 66 extending from the outer diameter end
of the bottom portion 10a in the axial direction is provided at the
center of the restricting member 10 in the circumferential
direction. The arm 66 is disposed between the separator 8 and the
inner circumferential face 5c of the outer ring 5 to prevent direct
contact between the separator 8 and the inner circumferential face
5c.
A face of the separator 8, which contacts the bottom portions 10a
of the restricting members 10 is preferably, a flat face. The
examples illustrated in FIG. 19 to FIG. 21 are based on the first
embodiment (FIG. 2), and the restricting member 10 is opened to one
axial side (right side in FIG. 19). Accordingly, on the opened side
of the restricting member 10, when the separator 8 moves in the
axial direction, the separator contacts the shield plate 9. Thus, a
ring for preventing direct contact between the separator 8 and the
shield plate 9 may be provided. Alternatively, a free end of the
arm 66 may be bent toward the inner radial side, and be hung on the
separator 8 to restrict movement of the separator 8 in the axial
direction.
The seventh embodiment is based on the first embodiment (FIG. 2) in
configuration of the restricting members 10, but may be based on
the second embodiment (FIG. 6). In this case, by displacing the
arms 66 in the circumferential direction, when the two restricting
members 10, 10' are disposed opposed to each other, the arms 66 do
not match in the axial direction and interfere with each other.
Alternatively, the arm 66 may be provided on one of the two
restricting members 10, 10'. In this case, however, two types of
restricting members are required.
Eighth Embodiment
Next, an eighth embodiment of the present invention will be
described with reference to FIG. 22 to FIG. 25a, FIG. 25b, and FIG.
25c.
A solid-lubrication rolling bearing 4 in the eighth embodiment has
the substantially same configuration as the solid-lubrication
rolling bearing 4 in the second embodiment (FIG. 6) in restricting
members 10. A difference is that, to prevent contact between the
separator 8 and the inner circumferential face 5c of the outer ring
5, the separator 8 and the restricting members 10 cooperate to
limit movement of the separator 8 in the radial direction.
More specifically, the separator 8 is similar to the separator 8
illustrated in FIGS. 9a to 9c in that the separator includes an
inner circumferential face 8a, an outer circumferential face 8b,
and a flat portion 8c, but is different from the separator 8
illustrated in FIGS. 9a to 9c in that the separator includes
protruding portions 53 on both axial end faces. The protruding
portions 53 extend in parallel to the inner circumferential face 8a
and accordingly, upper faces 55 (outer radial faces) extend in
parallel to the inner circumferential face 8a. A notch 66 for
receiving the protruding portion 53 of the separator 8 is formed at
the circumferential center on the inner periphery of the bottom
portion 10a of the restricting member 10. The protruding portions
53 of the separator 8 are inserted into the respective notches 66.
For convenience, the relation between the protruding portion 53 and
the notch 66 is referred to as male/female fitting.
As apparent from FIG. 22, due to the male/female fitting, the upper
faces 55 of the protruding portions 53 interfere with the upper
edges (outer diameter ends) of the notch 66, thereby preventing the
separator 8 from moving toward the outer radial side. That is, the
protruding portions 53 of the separator 8 and the notches 66 of the
restricting members 10 cooperate to restrict movement of the
separator 8 in the radial direction. This can prevent contact
between the separator 8 and the inner circumferential face 5c of
the outer ring 5.
As described above, the eighth embodiment is based on the
configuration in the second embodiment (FIG. 6) in the restricting
members 10, but may be based on the configuration in the first
embodiment (FIG. 2). In this case, it is desirable to make
male/female fitting between the separator 8 and the restricting
members 10 tight, to cause the restricting members 10 to hold the
separator 8. When the bottom portions 10a of the restricting
members 10 are disposed on both axial sides of the separator 8 as
in the second embodiment, male/female fitting between the separator
8 and the restricting members 10 can be achieved on both axial
sides, so that movement of the separator 8 in the axial direction
is restricted. Thus, in this case, male/female fitting may be
loose. However, when the restricting member 10 is disposed only one
axial side as in the first embodiment, the separator 8 is
cantilevered, and its free end may swing toward the outer radial
side to contact the outer ring 5.
Next, another embodiment of the solid lubricant forming the
separators 8 in the embodiment will be described. FIG. 26 is an
enlarged view illustrating microstructure of the solid
lubricant.
As illustrated in this figure, a solid lubricant 11 is a porous
body containing carbon material particles 12, graphite particles
13, a binder component 14 between the particles 12, 13, and pores
15. The carbon material particles 12 forms skeleton structure in
which the adjacent carbon material particles 12 are combined with
each other. The binder component 14 and the graphite particles 13
are held in the skeleton structure of the carbon material particles
12.
The solid lubricant 11 is formed by filling a forming die with
powder that includes carbon material powder, graphite powder, and a
binder to mold the powder into predetermined shape, and then,
removing the molded product from the forming die and firing it.
According to the present invention, amorphous and self-sintering
(ability to be sintered by itself) carbon material powder is used
as the carbon material powder. The carbon material powder is
different from crystalline graphite powder due to its amorphous
property, and is different from non self-sintering carbon fiber due
to its self-sintering property. Examples of the carbon material
powder include coke powder and pitch powder. Both of petroleum
pitch powder and coal pitch powder can be used as the pitch
powder.
Both of natural graphite powder and artificial graphite powder can
be used as the graphite powder. The natural graphite powder is
squamous and has excellent lubricity. The artificial graphite
powder has excellent moldability. Accordingly, the natural graphite
powder or the artificial graphite powder is selected according to
required characteristics. The graphite powder is crystalline before
and after firing. For example, phenol resin can be used as the
binder.
The above-mentioned carbon material powder and graphite powder are
granulated by adding the binder. Thereby, as illustrated in FIG.
27, granulated powder P in which carbon material powder 12' and
graphite powder 13' are held by a binder 14' is manufactured. The
carbon material powder 12' and the graphite powder 13' are fine
powder and have poor fluidity, and thus, cannot be smoothly filled
into the forming die. For this reason, they are granulated. The
granulated powder P having a particle size of 600 .mu.m or less
(average particle diameter of 100 .mu.m to 300 .mu.m) is selected
by pulverizing and filtering the granulated powder P.
The granulated powder thus obtained is supplied to the forming die,
and is pressed to mold a green compact. At this time, for the ratio
(weight ratio) of the carbon material powder 12', the graphite
powder 13', and the binder 14' in the green compact, the ratio of
the carbon material powder 12' is the highest, and the ratio of the
binder 14' is the lowest. Specifically, the carbon material powder
12' of 50 to 60 wt % and the graphite powder 13' of 25 to 40 wt %
are contained, and the remainder is occupied by binder 14' and
inevitable impurities.
Then, by firing the green compact, the solid lubricant 11
illustrated in FIG. 26 can be manufactured. The firing is performed
using inert gas such as nitrogen gas as atmospheric gas at
temperatures of 900.degree. C. to 1000.degree. C. in an oven.
Through the firing, the carbon material powder 12' becomes the
amorphous carbon material particles 12, and the graphite powder 13'
become the crystalline graphite particles 13. The binder 14'
becomes the binder component 14 that is amorphous carbon.
Preferably, the density of the sintered solid lubricant 11 is 1.0
to 3.0 g/cm.sup.3. When the density falls below the lower limit, a
crack tends to occur, and when the density exceeds the upper limit,
variation in size at molding (especially, variation in size in the
compressing direction) becomes large.
FIG. 28 illustrates microstructure of a solid lubricant containing
graphite as a main component in Patent literature 2. As illustrated
in this figure, in the conventional solid lubricant, the graphite
particles 13 are independent and are not combined with each other.
The binder component only holds the graphite particles 13, and is
not combined with the graphite particles 13. Thus, the material
strength is low, and the graphite particles tend to fall off. A
reference numeral 16 in FIG. 28 denotes an additive such as
tungsten.
On the contrary, in the solid lubricant 11 according to the present
invention, the carbon material particles 12 function as a base
material, and are combined with each other to form the skeleton
structure. The binder component 14 is amorphous and self-firing,
and thus, is combined with the carbon material particles 12.
Moreover, since the sintered carbon material particles 12 are hard,
the sintered solid lubricant 11 has high hardness. As a result, the
solid lubricant 11 has high material strength and hardness. The
graphite particles 13 hardly fall off. Therefore, the solid
lubricant having high lubricity as well as excellent impact
resistance and wear resistance can be obtained.
The hardness of the solid lubricant 11 of the present invention
reaches a Shore hardness (HSC) of about 50 to 100, and is much
higher that the hardness of the existing solid lubricant described
in Patent literature 2 (Shore hardness HSC: about 10 to 15). Due to
the hardness, the solid lubricant 11 of the present invention can
be machined later. The bending strength of the solid lubricant 11
of the present invention is 40 to 100 MPa, which is higher than the
bending strength of the existing solid lubricant a few to dozens of
times. The specific wear rate of the solid lubricant 11 of the
present invention is 1.0 to 2.5.times.10-7 mm.sup.3/(Nm) and is
one-hundredth of the specific wear rate of the existing solid
lubricant. Thus, the life of the bearing can be extended by using
the solid lubricant 11 of the present invention as the solid
lubricant disposed in the rolling bearing.
The skeleton structure of the carbon material particles 12 can be
replaced with a skeleton structure in which metal particles such as
Fe or Cu are combined with each other. However, this configuration
tends to be fragile due to oxidation. At elevated temperatures, the
material becomes soft, and both of material strength and hardness
are lowered, which makes it difficult to be used as the solid
lubricant. On the contrary, by adopting the skeleton structure of
the carbon material particles 12 according to the present
invention, oxidation and softening of the material at elevated
temperatures are hard to occur. Therefore, this configuration can
avoid such trouble.
Other composites can be added to the solid lubricant 11 as
necessary. For example, wear resistance can be improved by adding
at least one of W, Mo, and MOS.sub.2. This addition can compensate
lowering of wear resistance, which is caused by lowering of
lubricity of graphite at elevated temperatures. When the amount of
added composites is too large, material strength decreases. Thus, a
suitable amount is 1.0 vol % to 8.0 vol %.
To further improve wear resistance after firing, carbon fiber or
carbon nanotube can be added to the solid lubricant 11. However,
when the amount of the carbon fiber or carbon nanotube is too much,
moldability degrades. Thus, a suitable amount is 10 wt % or
less.
The separator 8 formed of the solid lubricant 11 having excellent
wear resistance can prevent premature wear of the solid lubricant,
and keep the lubricating effect of the solid lubricant 11 for a
long period. Since the amount of solid lubricant powder from the
separators 8 per unit time decreases, the amount of excess solid
lubricant powder in the bearing can be suppressed, so that leakage
of the solid lubricant powder can be more effectively prevented. In
addition, when the separators 8 become smaller due to wear after
long-term use, the rolling elements 7 collide with the thinned
separators 8. However, using the solid lubricant 11 having
excellent impact resistance can prevent damage on the separators 8
due to collision.
The present invention is not limited to the configuration in the
above-mentioned embodiments. Although the present invention is
applied to the deep groove ball bearing, the present invention can
be applied to other types of bearings including angular contact
ball bearings, and cylindrical roller bearings. Although the
outer-ring rotating rolling bearing 4 is illustrated in the
embodiments, the present invention can be also applied to an
inner-ring rotating rolling bearing.
The solid lubricant according to the present invention is described
to be used for the tenter clip bearing of the film stretching
machine. However, the solid lubricant can be applied to various
bearings (for example, bearings used in the ceramic industry) used
at elevated temperatures or in a vacuum, which prevents use of
grease or lubricating oil as the lubricant.
The rolling elements 7 and the separators 8 may be disposed in any
manner in the circumferential direction. In the first and the
second embodiments, a plurality of (for example, two) rolling
elements are used as one set, and one separator 8 is disposed
between the two adjacent rolling elements. The present invention
can be applied to the case where the rolling element 7 and the
separator 8 are alternately disposed in the circumferential
direction. Any number of rolling elements 7 and separators 8 may be
disposed between two restricting portions of one restricting
member.
REFERENCE SIGNS LIST
1: Guide rail 2: Frame 3: Clip 4: Solid-lubrication rolling bearing
5: Outer ring 5a: Outer raceway face 6: Inner ring 6a: Inner
raceway face 7: Rolling element (ball) 8: Separator 9: Sealing
member (shield plate) 10, 10': Restricting member 10a, 10a': bottom
portion 10a1, 10a1': inner side face 10b, 10b': restricting portion
10b1, 10b1' inner side face
* * * * *